Blades, U.S. Pat. No. 3,767,756, describes so-called air-gap spinning of anisotropic acid solutions of aromatic polyamides through a noncoagulating fluid, for example, air, and then into a coagulating liquid, for example, water. The spinnerets disclosed in Blades have a radial configuration of apertures and the filaments are coagulated in relatively still coagulating baths.
Yang, U.S. Pat. No. 4,340,559, describes a process improved over that disclosed in Blades. In Yang, the anisotropic spinning solution is passed through a layer of noncoagulating fluid, into a shallow, flowing, bath of coagulating liquid, and out of the bath through an exit orifice at the bottom of the bath, along with overflow coagulating liquid. The flow of coagulating liquid in the bath is nonturbulent but becomes turbulent at the site of localized jets arranged symmetrically about the exit tube and below but closely adjacent to the exit orifice. Moreover, flow of the coagulating liquid is increased by the force of the jets. Jets mentioned in Yang are radial or circular and are used to direct coagulating liquid in addition to the coagulating liquid which is caused to cascade, by free-fall, down the sides of the spin tube of small, circular, cross-section.
In the Yang apparatus, individual filaments are dragged over a solid lip or edge at the orifice from the bath.
European Patent Application 85/305646, published Feb. 19, 1986 as EP 172,001, discloses a process for spinning high-strength, high-modulus aromatic polyamide filaments using a free-falling coagulating bath. The filaments are produced by air-gap spinning an anisotropic solution of the polyamide in sulfuric acid, forming a single vertical warp of filaments, and conducting the filaments vertically downward into a gravity-accelerated and free-falling coagulating liquid. The coagulating liquid may be caused to be free-falling by passing the liquid over the edge of a continuously supplied reservoir so that the liquid forms a waterfall. After the filaments have been formed by contact with the coagulating liquid, they may be contacted with additional coagulating liquid such as by a side stream of liquid fed into the gravity-accelerated and free-falling coagulating liquid. Such a side stream may be fed into the existing stream in a nonturbulent manner and at about the speed of the filaments.
A "warp" is defined herein as an array of filaments aligned side-by-side and essentially parallel.